Hasil untuk "Radioactivity and radioactive substances"

Feifei Li, Qiang Liu, Wei Liu et al.

Natália Rocha Pinheiro, Francisco Bruno Souza Oliveira, Hermes Alves Filho

A semi-analytical nodal methodology is described in this paper for obtaining the numerical solution of eigenvalue problems based on neutron transport theory, in slab geometry, with isotropic scattering, using the discrete ordinates and multigroup energy formulation. This new approach applies a quadratic polynomial approximation only to the fission term in the transport equation, which justifies the method being classified as semi-analytical. The numerical solution is obtained through two interconnected iterative processes: the outer iterative process, which uses the power method to obtain successive estimates for the fission source and the effective multiplication factor ( ), and the internal iterative process, which aims to obtain successive estimates of the angular neutron fluxes emerging from the homogeneous regions throughout the spatial domain. Once the eigenvalues are calculated, for each outer power iteration, the angular fluxes of neutrons emerging at the node faces and in the sweeping direction of the internal iterative process are estimated. These are incoming fluxes at the faces of adjacent nodes, which ensures the continuity of the numerical solution. Computational algorithms were implemented in MATLAB. Numerical results for a typical benchmark problem considering an ADS, c.f., Accelerator-Driven Subcritical Reactor, type model are provided to illustrate the accuracy of the converged numerical solutions in coarse-mesh calculations. Although the method is not free from spatial truncation error, the results for the benchmark problem were considered satisfactory with one node per region, and refining the spatial domain did not result in a high computational cost in terms of response time, with results approaching those of analytical solutions.

Valentina Svitelman, Elena Saveleva

A. Castillo, N. A. Roas Zúniga

Quality controls are performed to verify the performance status of X-ray equipment in relation to image quality and patient dose. Originally, the Laboratory of Radiation Physics and Metrology (LAF-RAM) in Nicaragua had only one phantom to evaluate mammography image quality subjectively; however, under a cooperation project with the International Atomic Energy Agency (IAEA), the MAM-162 phantom was acquired for the evaluation of physical image quality. In this work a CR type digital mammography system was evaluated using the MAM-162 phantom with adaptation to a single quality control protocol based on international standards such as the German Institute for Standardization (DIN) DIN 6868-162:2013-06, the IAEA technical document TECDOC protocol No. 1958 and the European Federation of Organizations for Medical Physics (EFOMP) mammo protocol. Among the main tests performed are the evaluation of the lateral image limit of the chest wall with satisfactory results, the automatic exposure control, the Signal-to-Noise difference ratio that complies with the tolerances, in the case Ghosting and dynamic range the results of both are satisfactory, the presence of artifacts was observed when applying variance mapping, a base value of the dynamic range was also obtained. For the dosimetry, the half value layer and the determination of the Mean Glandular Dose were evaluated, which does not comply with the tolerances. The final protocol document could be validated and implemented as part of the management and service documents of the Quality Control and Monitoring Laboratory (LCM) of LAF-RAM.

Leo Sousa Santiago de Oliveira, Luiza Freire de Souza, Gabriela Guimarães Donald et al.

Thermoluminescent (TLD) and optically stimulated luminescent dosimeters (OSLD) are essential in radiation dosimetry. Such dosimeters can be easily transported due to their small size and can be used in in vivo dosimetry and anthropomorphic simulations. In this work, the dosimetric properties of Li2B4O7 and MgB4O7 compounds were evaluated based on their response to the applied stimulus, whether thermal or optical. The linear dose response range of the luminescent signal, its fading, the lowest detectable dose, and reproducibility are important parameters in determining a good dosimeter for clinical and personal dosimetry. Therefore, the objective of this work was, based on studies performed by other authors on dosimetric characterizations of doped a codoped Li2B4O7 and MgB4O7, to point out those compounds with the greatest potential for applications in personal and clinical dosimetry using TL and OSL techniques. Considering the results described in other works, the materials that stood out for use in personal and clinical dosimetry were Li2B4O7:Cu and MgB4O7:Dy,Na. In several of the reported studies, no data related to LDD, fading and reproducibility of the luminescent signal of the investigated compounds were found. Therefore, there are many possibilities for investigations into these two types of compounds for the purpose of their use in personal and clinical dosimetry. Further studies will provide a broader scientific basis for choosing appropriate dosimetric materials for these applications.

Vanessa Sanches Pereira da Silva, José Roberto Ferreira Neto, Silvia Lucas Ferreira da Silva et al.

Maraging steels are martensitic steels hardened by precipitation during thermal aging, with good machining properties and high strength and corrosion resistance. It is well suited for applications which require high strength-to-weight material, being used in aerospace, aeronautics and nuclear industries. A protective and corrosion resistant oxide layer can be formed during age hardening if treated in steam atmosphere. This work aims to use grazing incidence X-ray diffraction (GIXRD) to evaluate qualitatively the thickness of the layers formed during this process. GIXRD and scanning electron microscopy (SEM) were employed to identify and order the layered structure formed on four specimens of maraging steel grade 300 with different surface finishes that were previously solution annealed twice at (950 ± 5) °C for 1 h, air-cooled, and submitted to oxidation process under positive pressure around 1.5 kPa of steam at (480 ± 5) °C for 6 h followed by forced air cooling. The diffraction patterns were measured employing CuKα radiation and parallel beam, in step scan mode, using incident angles varying from 0.2º to 4.0º and 20º < 2θ < 85º. The results revealed the formation of two layers, the innermost was formed by γ-iron (austenite – fcc) phase followed by a mixture of oxides (hematite and magnetite) on the top, regardless of surface finish, which was confirmed by the SEM analysis that also allowed the measurement of the average layer’s thickness of oxides (1.130 ± 0.094) µm and austenite (0.507 ± 0.090) µm phases, and corroborated the qualitative thicknesses analysis made from GIXRD results.

Marcela Ferreira Freitas, Cesar Marques Salgado

Most of the natural gas production is transported through pipelines that require periodic inspections to evaluate the structural integrity of the pipelines due to possible defects caused by degradation that can rupture causing leakage of the fluid causing major disasters. Based on this, the project presents a methodology for predicting cracks in pipe used in gas pipelines. The approximation is based on the principles of gamma densitometry to calculate the density of the pipe wall in order to investigate possible cracks. The natural gas fluid is found in such systems and interferes in the density calculations and therefore will be considered in the simulations. The detection system uses a narrow beam geometry appropriately, comprising gamma ray source (137Cs) and NaI(Tl) 3"x3" detectors for calculating transmitted and scattered photons. Different positioning angles of the detector are investigated.  In this study, the MCNP-X code is used to perform the simulations, in order to develop a counting geometry. Simulations of different thicknesses of the crack were also used to determine the minimum thickness detected by the two NaI(Tl) detectors. Having equipment that can estimate cracks present in pipes used in gas pipelines, in addition to predicting their location can reduce costs and make a major contribution to this sector.

Isabela Rodrigues Rigo, Ana Paula Vollet Cunha, Caroline Zeppellini dos Santos Emiliozzi et al.

The formalism used for barriers calculations is based on a conservative estimation of workload, use factor, and occupancy factor. IMRT techniques (Intensity Modulated Radiation Therapy) and VMAT (Volumetric Modulated Arc Therapy) are known for being superior to conventional techniques, but costly from the shielding standpoint, as they increase the number of monitor units used to deliver the same dose to the patient, increasing the leakage radiation produced and, consequently, the thickness of the secondary barriers. At InRad (Radiology Institute of HC-FMUSP) a 2100CD LINAC already installed was upgraded to perform IMRT/VMAT techniques, and the existing barrier was reassessed. The present study proposes a methodology for acquiring real workload data from the institution's management software (MOSAIQ®) to replace the initially estimated data and recalculate the thickness of the barriers, assessing the impact of the introduction of these techniques and understanding the profile of the treatments carried out at the institution over the years of 2010 to 2020. Through this methodology, a decrease in the workload of 15 MV was observed as the technique of modulated intensity with 6 MV was introduced, reducing the thicknesses calculated for primary barriers. However, no significant changes were observed in the thicknesses calculated for the secondary barriers, because despite the increase in the leakage workload of 6 MV, the total workload of 15 MV decreased. There was also a trend towards an increase in the number of patients treated with modulated intensity year after year, which went from 5% in 2016 to 67% in 2020.

Vitor Jesus Oliveira, Ana Cristina Dovales, Delano Valdivino Batista et al.

O tratamento de linfoma de Hodgkin com radioterapia tem sido aprimorado nas últimas décadas de forma a minimizar os efeitos colaterais danosos da radiação ionizante no paciente. Um novo desafio que surge é a análise da dose em órgãos fora da região de tratamento e o risco atribuído a essa exposição. Neste trabalho avaliamos as doses nos órgãos de interesse e o risco subsequente de indução de câncer após o tratamento. Foi feita a simulação de um tratamento em uma paciente feminino de 20 anos, para avaliação do risco de desenvolvimento de câncer secundário após a exposição à radiação. Para isso, utilizamos o fantoma feminino e o acelerador linear Clinac® iX 885 da Varian para a calibração dos TLDs e irradiação do fantoma. O programa online RadRAT foi usado para avaliar o risco ao longo da vida. Foi feita a comparação entre cinco países cujas informações sobre expectativa de vida e taxa de incidência de câncer estão registradas no programa. Nossos resultados mostraram que o tratamento convencional para o linfoma de Hodgkin acarreta um risco atribuído maior para o  desenvolvimento de câncer no cérebro aumentando entre 21% e 23% o número de novos casos. Para câncer no útero, o excesso de risco é pouco maior que 2%, não tendo um aumento estatisticamente significante (p=0,30). O câncer de bexiga, no entanto, apesar de ser o órgão mais distante do campo de irradiação teve um risco atribuído ao longo da vida próximo a 10% na maioria dos grupos populacionais.

Masakazu Ota, Taku Tanaka

A. E. Lomovtsev, T. E. Sheveleva, A. S. Karpukhin et al.

Aim of the study: analysis of the results of the radiation-hygienic monitoring of the territories of the Tula region, contaminated due to the Chernobyl NPP accident; concentration of 137Cs and 90Sr in the locally produced food products and analysis of the annual effective dose of the public. Materials and methods: the study was performed in the Tula region in 1997-2018. It included the evaluation of the indicators of the radiation safety of more than 50 thousand samples of the main food products, sampled in the areas of the radioactive “Chernobyl” contamination of the region with the simultaneous measurement of the external gamma-radiation dose rate in the stationary control points. Additionally, it included the assessment of the dynamics of concentration of 137Cs and 90Sr in food products, maximal values of mean annual effective doses of the public and contribution of the collective dose from medical exposure into the structure of the annual collective dose of the public. Results: The study allowed estimating the concentration of 137Cs and 90Sr in the main local food products. Estimated values of gamma radiation dose rate were stable and laid in the range of normal variations specific to the middle latitudes of the European part of Russia. The values of maximal mean annual effective doses of the public indicate the stable radiation environment and do not exceed 1 mSv. It should be mentioned that the contribution of collective dose from medical exposure into the annual collective dose of the public as well as the values of mean individual effective doses from medical exposure are reducing with the increase in the number of X-ray examinations. Conclusions: The lack of exceedances of the permissible levels of 137Cs and 90Sr in the locally produced food products and the reduction of the mean annual effective dose of the public indicates the possibility of the transfer of the settlements affected by the Chernobyl NPP accident into the normal living conditions within the program of the transfer of the settlements from the “Chernobyl” zone.

Denise Aparecida da Silva Rios, Paulo Beolchi Rios, Gian-Maria Agostinho Angelo Sordi et al.

Este estudo tem por finalidade estimar as doses decorrentes de situações de exposição potencial em uma indústria de embalagens que utiliza um acelerador de elétrons autoblindado para a cura de tintas e vernizes em substratos poliméricos. Para isso foram avaliadas as probabilidades de falhas no sistema de segurança do acelerador e realizadas simulações envolvendo duas situações acidentais que poderiam levar à exposição potencial de Indivíduos Ocupacionalmente Expostos e Indivíduos do Público. Embora estas situações de exposição sejam pouco prováveis e envolva um número pequeno de indivíduos o estudo ressalta a importância de realizar exercícios de simulação permitindo identificar as possíveis falhas de operação e as consequências radiológicas para esse tipo de evento. Os exercícios de simulação realizados apontaram a necessidade de incluir os participantes da brigada de incêndio nos treinamentos periódicos de proteção radiológica. Além disso, as estimativas de probabilidade de falha no sistema de segurança e as doses resultantes indicaram o enquadramento desse tipo de equipamento aos critérios regulatórios para isenção dos requisitos de proteção radiológica.

Mauricio Gomez, Priscila do Carmo Santana, Arnaldo Prata Mourão

Non-invasive diagnosis methods based on x-ray attenuation, such as Computed Tomography (CT) has had since its discovery and the development of this technology, a rapid growth in radiology services. The quantity of dose deposited in patients, is still large, this type of examination is that reaches the highest levels of absorbed dose in the population. Legislation that regulates the levels of patient’s dose is only limited to a maximum amount deposited, depending the body region to be irradiated.  Therefore, it is necessary to determine the amount of absorbed dose on patients depending on the protocols of routine used in radiology services for propose an optimization of these based on the principles of radiation protection. Experiments were conducted to determine the profile of dose deposited in head routine exams for adult, using a cylindrical head phantom made of polymethylmethacrylate (PMMA). This standard phantom has four openings in peripheral and one central. Radiochromic film strips were introduced into each one of these openings to register the longitudinal dose profile in each region to determine the amount of deposited dose in the volume of the head phantom. A CT scanner with 64 channels of GE from the radiology department was used for scanning the head phantom. The scanning were done with voltages of 80, 100 and 120 kV, and dose index found were between 6.24 and 23.73 mGy. Analysis of image quality was performed, finding that all scan comply with the parameters acceptable in diagnosis for Brazilian legislation. It is propose an optimized protocol for exams by CT head for the voltage of 80 kV and images with 0.5% of noise index.

Seung Min Lee, Nelbia da Silva Lapa, Gaianê Sabundjian

The aim of this work was to simulate a severe accident at a typical PWR, initiated with a break in Emergency Core Cooling System line of a hot leg, using the MELCOR code. The model of this typical PWR was elaborated by the Global Research for Safety and provided to the CNEN for independent analysis of the severe accidents at Angra 2, which is similar to this typical PWR. Although both of them are not identical, the results obtained of that typical PWR may be valuable because of the lack of officially published simulation of severe accident at Angra 2. Relevant parameters such as pressure, temperature and water level in various control volumes, after the break at the hot leg, were calculated as well as degree of core degradation and hydrogen production within the containment. The result obtained in this work could be considered satisfactory in the sense that the physical phenomena reproduced by the simulation were in general very reasonable, and most of the events occurred within acceptable time intervals. However, the uncertainty analysis was not carried out in this work. Furthermore, this scenario could be used as a base for the study of the effectiveness of some preventive or/and mitigating measures of Severe Accident Management by implementing each measure in this model.

Liliana Castro, Edson Gonçalves Moreira, Marina Beatriz Agostini Vasconcellos

The minimum sample intake for which a reference material remains homogeneous is one of the parameters that must be estimated in the homogeneity assessment study of reference materials. In this work, Instrumental Neutron Activation Analysis was used to evaluate this quantity in a bovine kidney candidate reference material. The mass fractions of 9 inorganic constituents were determined in subsamples between 1 and 2 mg in order to estimate the relative homogeneity factor (HE) and the minimum sample mass to achieve 5% and 10% precision on a 95% confidence level. Results obtained for HE in all the analyzed elements were satisfactory. The estimated minimum sample intake was between 2 mg and 40 mg, depending on the element.

Janete C. G. Carneiro, Alice S. Alves, Demerval L. Rodrigues et al.

The occupational risk assessment is a structured and systematic process, which depends on the correct identification of probable risk factors and agents potentially founded at workplace. The objective of this paper was to carry out the basic characterization of a Brazilian radioisotope production facility through ample knowledge of the workplace, workforce, task performed and identification and evaluation of occupational risk agents in the workplace. The data analysis comprised a qualitative or quantitative approaches based on subjective information obtained by questionnaire, interview and observations about workplace, workforce and risk agents. The workforce was distributed into eight work processes. Regarding task-related exposure there was assumed that all workers presented the same exposure profile. Therefore, it was made an evaluation of the association degree between the occupational risks agents, which there were identified 17 risk agents at the workplace, including physical, chemical, biological, ergonomic and accident risks. Although the workers may be potentially exposed to different risk agents, the ionizing radiation was the main physical risk factor observed in this facility.  

A. M. Biblin, R. R. Akhmatdinov, K. V. Varfolomeeva et al.

Presumably in the first days of April 2013, the smelting of scrap metal occurred on the territory of the Electrostal Heavy Engineering Works without the use of radiation input control. An unspecified source of ionizing radiation, containing 137Cs in an unknown quantity, was melted. As a result of smelting, contamination of the territory of the plant and the adjacent territory of Elektrostal city occurred. The relevance of the study is due to the high social significance of this accident, which is confirmed by a large number of materials published in both federal and regional mass media. In total, for the period from 12.04.2013 to 12.05.2013, 129 materials were identified. In addition, the total number of video views on this accident on the YOUTUBE website exceeds the population of Electrostal city. The purpose of the study was to analyze the practice of crisis risk communication, used by various officials and specialists in connection with the radiation accident in the territory of the Electrostal Heavy Engineering Works in 2013. The study analyzed publications in the mass media, messages on official websites of departments, organizations and authorities involved in the emergency response, video materials on the YOUTUBE website, messages on Internet forums. In order to record, analyze and store publications, an automated information system for the analysis of publications, developed by specialists of the Rospotrebnadzor Information and Analytical Center for Radiation Safety of the Population was used. The analysis of crisis risk communication with the population conducted by government bodies and representatives of various departments in the liquidation of the consequences of a radiation accident on the territory of the Electrostal Heavy Engineering Works revealed a discrepancy between the real risk communication practices in the case of the radiation accident in Elektrostal with modern scientific recommendations for radiation risk communication. Individual cases of unreliable and mutually exclusive information provided by the authorities to citizens were identified, resulting in a rather negative response on the part of Internet users. As a result of the research, there was revealed a lack of response to information materials distributed on the Internet, devoted to a radiation accident on the part of official authorities. Information from the authorities aimed at appeasing the public, due to the critical perception of the information received from the authorities, was not taken seriously by a significant part of the population. It was shown that in order to reduce the negative consequences of ineffective information work with the public, it is necessary to develop methodological support for crisis risk communication and to introduce it into the everyday practice of Rospotrebnadzor through training and improving the skills of individuals involved in communication with the media, non-governmental organizations and the population.

O. N. Prokof 'ev

The radionuclide 89Sr give considerable contribution in the composition of fission products, which get in environment due to an accident of nuclear reactor or due to conducting of peaceful nuclear explosion. By radiation characteristics this radionuclide essentially differs from 90Sr. Due to its shorter half period it faster leaves the objects of environment and therefore represents less radiation hazard for man than 90Sr. These radionuclides belong to the same element of chemical system and therefore are difficulty separated with the use of chemical methods. The work offers an approach, which joins chemical and radioactive methods.

V. I. Evdokimov, I. B. Ushakov

Science Index system for information analysis is one of effective modern indexes of innovative activity of Russian research and educational personnel, research and educational institutions. However, it should be noted that this assessment system does not yet include such important parameters as data on patent analysis and dissertation research. The article describes information search and preliminary bibliometric assessment of publication activity of the authors and some research institutions and periodicals in the field of radiation hygiene and medicine.

I. G. Shatskii

Regional study was conducted in 12 specialized pediatric medical organisations in St. Petersburg to assess exposure levels of pediatric patients (newborns, 1, 5, 10 and 15 years) during the most common radiographic examinations. The average values of effective doses for each age group, as well as the minimum and maximum average effective dose for the X-ray machine for each type of examinations and quantiles of dose distributions are provided. The ratio of the maximum to minimum dose values for the different of X-ray apparatuses, in most cases, was found to be a factor of 15. The average effective doses for the projection in the hospitals of St. Petersburg are compared with the similar data from Italian hospitals.